Electrostatic spray guns having self-contained power supplies such as shown in U.S. Pat. Nos. 4,554,622, 4,462,061, 4,290,091, 4,377,838 and 4,491,276 are well known. Such applicators have an air-powered turbine which drives an alternator which in turn supplies a voltage multiplier to provide the charging voltage.
In such products, the bearings are used to hold and allow a magnet to rotate on its shaft. In normal operation, air is passed over an internal impeller causing the magnet to rotate and such rotation inside a coil of wire provides electrical power for the applicator. This air is then exhausted through a separated air passage to the outside of the applicator. Such placement of the bearings inside the applicator allow the passage of air over and around the bearings to remove slight amounts of lubricant from the bearings. Because of this lubricant, this exhaust air must be separated from the air that is used to atomize the paint in order to prevent contamination with the bearing lubricant.
During cleaning of the applicator with solvents, such liquid solvents can flow into the bearings through the air passages, causing the solvents to remove the lubricant from the bearings subsequently leading to bearing failure. Also, if the air cap was not properly tightened, paint can flow backwards in the applicator filling the alternator air passages and the bearings with paint thereby forcing the alternator to be removed and replaced.